The present invention pertains to an absorbent article, such as a disposable diaper, sanitary napkin, adult incontinence garment, training pant or the like, which includes a pH control agent to help maintain prolonged natural skin pH.
Commonly, an absorbent article, such as a disposable diaper, adult incontinent garment, training pant or sanitary napkin, comprises a topsheet which is at least partially liquid permeable, a liquid-impermeable backsheet, and an absorbent core formed from (1) cellulosic fibers, which typically are comminuted softwood pulp fibers, and (2) distributed particles of a superabsorbent polymer (SAP). The absorbent core is generally positioned between the topsheet and the backsheet. It is known to provide the absorbent article with one or more other layers formed from cellulosic fibers or other materials to perform various liquid-absorbing, liquid-distributing, and cushioning functions.
A persistent problem associated with the use of such an absorbent article is xe2x80x9cdiaper rashxe2x80x9d, a common form of irritation and inflammation of those parts of user""s body normally in contact with the, absorbent article. It is generally accepted that true xe2x80x9cdiaper rashxe2x80x9d or xe2x80x9cdiaper dermatitisxe2x80x9d is a condition which is, in its most simple stages, a contact irritant dermatitis. The irritation of simple diaper rash results from extended contact of the skin with urine, or feces, or both. The most commonly accepted list of factors linked to diaper rash includes ammonia, bacteria, the products of bacterial action, urine pH, Candida albicans, and moisture.
More specifically, a primary cause of diaper rash is believed to be a particular set of conditions which arises as a result of prolonged contact of skin with mixtures of feces and urine. Activity of proteolytic and lipolytic fecal enzymes present in such a mixture is believed to be a major factor in producing skin irritation. Further, urease excreting bacteria facilitate the degradation of urea into ammonia, thereby increasing the pH of urine and fecal matter which in turn raises skin pH. This rise in skin pH, for example to levels of 6.0 and above, increases the fecal proteolytic and lipolytic enzymatic activity which may produce diaper rash. Urine itself can also contribute to diaper rash by adding moisture to the diaper environment. Water, and particularly water in the form of urine, is especially effective at diminishing the barrier property of skin, thereby enhancing the susceptibility of skin to fecal enzyme irritation. However, when skin pH is kept at natural levels, i.e., between about 4.5 and about 6.0, the skin""s barrier properties can be maintained.
The foregoing diaper rash model suggests that effective diaper rash control can be achieved by maintaining natural skin pH to thereby inhibit irritation-producing enzymatic activity while simultaneously maintaining the absorbent article environment as dry as possible.
Absorbent articles, compositions and procedures which incorporate buffers and/or acidifying agents into absorbents articles for controlling skin pH are known. For example, see U.S. Pat. No. 4,685,909 to Berg et al. (xe2x80x9cBergxe2x80x9d). Berg discloses absorbent articles having acidic pH control agents and absorptive hydrogel materials non-uniformly distributed in distinct, discrete zones within the absorbent article. Berg teaches that the simple combination of pH control agents and absorptive hydrogel materials is not desirable, and that instead the components should be separated into discrete zones. By separating hydrogel materials and pH control agents in this manner, Berg concludes that skin pH can be controlled in the presence of urine and fecal matter to combat diaper rash without adversely affecting the ability of the hydrogel to absorb fluids and maintain skin dryness. Further, Berg teaches that the pH control agents should be present at relatively high levels ranging from about 1% to 30% by weight, based on the total weight of the absorbent article. Therefore, the absorbent article taught by Berg is disadvantageous in that it requires the presence of relatively large amounts of pH control agents. Further, the manufacturing processes are complicated by the necessary steps involved in separating the pH control agent from the absorbent material in the core.
Another approach in the prior art for combating diaper rash is the incorporation of a pH control agent into a lotion which is then deposited on the topsheet of an absorbent article. For instance, U.S. Pat. No. 5,525,346 to Hartung et al. discloses a diaper wherein at least a portion of the diaper that will contact the user""s skin is impregnated with a lotion that includes a pH control agent. Further, the pH control agent is preferably included in the lotion in an amount of at least 3.5% by weight, based on the total weight of the lotion. Again, such a lotioned diaper is cumbersome in that the manufacturing process is complicated by the inclusion of additional steps necessary for applying the lotion to the diaper. Further, such a lotioned diaper is economically burdensome due to the increased costs associated with the additional processing steps, and the lotion itself.
Therefore, among other things, this invention has resulted from ongoing efforts to produce an absorbent article which is capable of maintaining natural skin pH in an effective, prolonged, and economical manner.
Accordingly, an object of the present invention is to provide an absorbent article which comprises a pH control agent to maintain prolonged natural skin pH.
Another object of the present invention is to provide an absorbent article comprising a topsheet, wherein at least a portion of the topsheet includes a pH control agent, such as citric acid or sodium citrate, in an amount sufficient to maintain prolonged natural skin pH.
The invention further relates to an absorbent article comprising a topsheet and an absorbent core wherein at least a portion of the topsheet and at least a portion of the absorbent core include a pH control agent in an amount sufficient to maintain prolonged natural skin pH.
These and other objects, features and advantages of this invention are evident from the following description of a preferred embodiments of this invention, with reference to the accompanying drawings.